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Chinese Journal of Chromatography
2018, Vol. 36, No. 5
Online: 08 May 2018

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Fast determination of betaine in Lycii Fructus by ultra-performance convergence chromatography-tandem mass spectrometry ZHANG Xianfei, YANG Junli, CHEN Juan, SHI Yanping 2018, 36 (5):  417-424.  DOI: 10.3724/SP.J.1123.2017.12020 Abstract ( 448 )   [Full Text(HTML)] () PDF (838KB) ( 71 )   Over the past 2500 years, Lycii Fructus has been widely used as a functional food and tonic in Chinese herbal medicine. It can nourish the liver and kidneys, moisten the lungs, and improve eyesight. In this study, a new rapid and sensitive method has been developed for the quantitative determination of betaine (index compound) in Lycii Fructus by using ultra-performance convergence chromatography-tandem mass spectrometry (UPC2-MS). The separation of betaine was successfully achieved on an ACQUITY UPC2 BEH 2-EP column (150 mm×2.1 mm, 1.7 μm), with isocratic elution by a CO2-methanol (80:20, v/v) solvent at a flow rate of 0.7 mL/min. The conditions used in the separation process were as follows:modifier, 0.1% (v/v) formic acid in methanol; column temperature, 40℃; backpressure, 1.31×107 Pa; injection volume, 1 μL; and retention time, 3 min. The MS system was equipped with an electrospray ionization (ESI) ion source and operated in the selected ion recording (SIR) and positive ion mode. Under the abovementioned conditions, the calibration curve was obtained. The linear range of detection was 0.5-50.0 μg/mL, with a correlation coefficient of 0.9992, and the limit of detection (LOD) was found to be 0.013 μg/mL. The validity of the method was tested by analyses of precision, repeatability, stability, and accuracy (average recovery:96.3%). Finally, the developed method was applied to analyze 11 batches of samples. The results indicated that this method was suitable for evaluating the quality of Lycii Fructus.

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Determination of 15 functional components in sweet potato leaves by ultra high performance liquid chromatography-tandem mass spectrometry ZHOU Shaohuan, LIANG Chuan, TANG Yang, LIAO Yanhua, LIN Wensi 2018, 36 (5):  425-430.  DOI: 10.3724/SP.J.1123.2017.11046 Abstract ( 437 )   [Full Text(HTML)] () PDF (791KB) ( 62 )   A method for the rapid determination of 15 functional components in sweet potato leaves by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was established. The samples were extracted with 80% (v/v) methanol aqueous solution, and then separated on a C18 column (100 mm×2.1 mm, 1.8 μm) with gradient elution. The mobile phases were acetonitrile and 0.15% (v/v) formic acid aqueous solution. The multiple reaction monitoring (MRM) mode was used to detect the molecular ion peak of each component in electrospray ionization (ESI) source and negative ion scan mode. The results showed that the good linear relationships for the 15 components were obtained with correlation coefficients (r) ranging from 0.9995 to 0.9998. The recoveries of all the components ranged from 82.2% to 131.4% with relative standard deviations of 3.6%-8.3%. The method is simple, sensitive, and is suitable for the rapid analysis of the functional components in sweet potato leaves.

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Determination of nitroimidazoles and their metabolites in animal-derived foods by liquid chromatography-tandem mass spectrometry coupled with dispersive solid phase extraction FANG Li, QIU Fengmei, YU Xinwei, ZHANG Zhichao 2018, 36 (5):  431-438.  DOI: 10.3724/SP.J.1123.2017.12028 Abstract ( 437 )   [Full Text(HTML)] () PDF (2727KB) ( 99 )   A method for the quantitative analysis of nitroimidazoles and their metabolites in four kinds of animal-derived foods by liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with dispersive solid phase extraction (dSPE) was established. The samples (2.0 g) were extracted with ethyl acetate. The extracts were degreased with hexane and purified with 50 mg primary-secondary amine (PSA), and then filtered through a hydrophilic polytetrafluoroethylene (PTFE) membrane. The analytes were separated on a C18 column, and detected in selected reaction monitoring (SRM) mode via positive electrospray ionization. The matrix matching and internal standard method was used. The nitroimidazoles and their metabolites showed good linearity in the range of 0.5-20.0 μg/L with correlation coefficients greater than 0.99. The limits of detection of the nitroimidazoles and their metabolites in animal-derived foods were between 0.1 and 0.5 μg/kg. The recoveries varied between 84.2% and 120.8%, with relative standard deviations (n=6) ranging from 2.0% to 16.2% at spiked levels of 1.0, 3.0, and 10.0 μg/kg. The proposed method is accurate, fast, cheap, easy, and can satisfy the requirements of monitoring nitroimidazoles and their metabolites in animal-derived foods.

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Simultaneous determination of six aflatoxins and sterigmatocystin in livestock and poultry tissues by QuEChERS-ultra high performance liquid chromatography-tandem mass spectrometry LING Aru, GUO Wenbo, YANG Junhua, ZHAO Zhihui, GUO Jinli 2018, 36 (5):  439-445.  DOI: 10.3724/SP.J.1123.2017.11028 Abstract ( 394 )   [Full Text(HTML)] () PDF (1581KB) ( 71 )   A method for the simultaneous determination of six aflatoxins (AFTs) and sterigmatocystin (SMC) in livestock and poultry tissues by QuEChERS-ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed and validated. The samples were extracted with 10 mL acetonitrile-water (84:16, v/v) after enzymatic hydrolysis with 20 μL β-glucosidase. The extracts were cleaned with 1.0 g each of sodium chloride and anhydrous magnesium sulfate, and then degreased with 5 mL hexane. The residues were re-dissolved in 1 mL acetonitrile-water (80:20, v/v) containing 5 mmol/L ammonium acetate. Methanol and 5 mmol/L ammonium acetate were used as the mobile phases. Six AFTs and SMC were analyzed by multiple reaction monitoring in the positive ion mode. Matrix-matched calibration curves and external standards were used for the accurate quantification of the six AFTs and SMC. Good linear relationships were obtained, the correlation coefficients (R2) were greater than 0.99. The limits of detection (LODs, S/N=3) and the limits of quantification (LOQs, S/N=10) ranged from 0.007 to 0.30 μg/kg, and 0.02 to 0.91 μg/kg, respectively. The recoveries at different spiked levels were satisfactory, and ranged from 77.3% to 118.5%. This method is simple, easy and sensitive, and is suitable for the rapid determination of the six AFTs and SMC in different pork, pork liver and chicken samples.

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Determination of 3-methylquinoxaline-2-carboxylic acid of olaquindox marker residue in chicken muscles by liquid chromatography-tandem mass spectrometry LI Erfen, ZHANG Meiyu, MA Heqin, ZHANG Jiahui, LIU Rong, ZENG Zhenling, HE Limin 2018, 36 (5):  446-451.  DOI: 10.3724/SP.J.1123.2017.12023 Abstract ( 361 )   [Full Text(HTML)] () PDF (1114KB) ( 94 )   A simple, sensitive, scientific and reproducible liquid chromatography-tandem mass spectrometric method was developed to determine 3-methylquinoxaline-2-carboxylic acid (MQCA) of olaquindox marker residue in chicken muscle tissues. The chickens were administered orally with olaquindox and used as positive samples. The approaches, enzyme, acid, and base hydrolysis, were adopted to digest MQCA in the medicated chicken muscles. The amounts of MQCA in the medicated chicken were determined and compared using different hydrolysis approaches. It was shown that the highest amount of MQCA was obtained for the base hydrolysis approach. Here, the sample was hydrolyzed with 1.0 mol/L NaOH solution, defatted with n-hexane, and purified with a mixed anion-exchange solid-phase extraction cartridge. The chromatographic separation was performed on a reversed-phase C18 column and detected using mass spectrometry in selected reaction monitoring mode. The analyte showed good linearity in the range 1.0-100 μg/L. The correlation coefficient (r2) was greater than 0.99. The limit of detection of the proposed method was 0.4 μg/kg. At the three spiked levels of 1.0, 5.0 and 50.0 μg/kg, the average recoveries of MQCA were in range 71.7%-82.4% obtained using external standard calibration, and in range 96.3%-103.7% for internal standard calibration, with relative standard deviations below 6.0%. The proposed method is suitable for routinely monitoring of MQCA residues in animal-derived foods.

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Determination of phthalates in water by dispersive liquid-liquid microextraction based on solidification of floating organic drop followed by high performance liquid chromatography WU Cuiqin, LI Ying, CHANG Shuping, CHEN Yongheng, CHEN Diyun, GONG Jian, XU Liangzhi 2018, 36 (5):  452-457.  DOI: 10.3724/SP.J.1123.2017.11060 Abstract ( 424 )   [Full Text(HTML)] () PDF (1225KB) ( 78 )   A rapid method for the determination of six phthalates (PAEs) in water samples was established by dispersive liquid-liquid microextraction (DLLME) based on solidification of floating organic drop (SFO) coupled with high performance liquid chromatography (HPLC). The influences of the SFO-DLLME parameters on extraction efficiencies were studied. Dodecanol (extraction solvent, 20 μL) was added to the water samples (containing 20 g/L NaCl) at 60℃, and the solution was shaken for 1 min. The results showed that the six PAEs were linear in the range of 2-2000 μg/L with correlation coefficients (r) between 0.9995 and 0.9999. The limits of detection (S/N=3) of the six PAEs ranged from 0.3 to 0.6 μg/L. The proposed method was applied to the analysis of the seven water samples obtained from different sources (tap water, lake water, river water, waste water, sea water, plastic bottled pure water and mineral water), and some PAEs were detected. The recoveries of the six PAEs in the spiked water samples were 84.9%-94.5%, and relative standard deviations were 4.1%-6.8% at three levels of 10, 100 and 1000 μg/L. The method is an environmentally friendly and convenient method for the routine analysis of the PAEs in water samples.

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Dispersive liquid-liquid microextraction based on molecular complexation followed by high performance liquid chromatography for the determination of two phenoxy carboxylic acid herbicides in environmental water samples ZHANG Jiping, JIANG Xindi, HUANG Wei, QIN Qian, ZHOU Qiao 2018, 36 (5):  458-463.  DOI: 10.3724/SP.J.1123.2017.12021 Abstract ( 325 )   [Full Text(HTML)] () PDF (1471KB) ( 96 )   A dispersive liquid-liquid microextraction (DLLME) method based on molecular complexation was developed for the determination of 2,5-dichloro-6-methoxybenzoic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-D) in environmental water samples by high performance liquid chromatography-ultraviolet detection (HPLC-UV). Tri-n-butylphosphate (TBP) and methanol were selected as the extraction solvent and dispersive solvent, respectively. Parameters affecting the extraction efficiency, including the type and volume of the extraction and dispersive solvents, pH of the sample solutions, pH of the backward extraction solution, and salt addition, were optimized. Under the optimized conditions, the linear range was 0.50-1000 μg/L for the two target herbicides. The limits of detection (LODs, S/N=3) were 0.44 μg/L and 0.49 μg/L for dicamba and 2,4-D, respectively. The enrichment factors (EFs) of dicamba and 2,4-D were 85 and 90, respectively. The recoveries were in the range 75.7%-104.0%. The proposed microextraction involved molecular complexation, and the Lewis acid-base interactions between TBP and the acidic herbicides gave satisfactory extraction results. Thus, the method is expected to be a powerful tool for the determination of acidic herbicides in environmental water samples

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Separation of lignans from Schisandra chinensis by two-dimensional reversed-phase liquid chromatography ZHU Jingbo, LI Wenyu, XIAO Wei, DING Yan, HUANG Wenzhe, TU Pengfei, WANG Yonghua 2018, 36 (5):  464-473.  DOI: 10.3724/SP.J.1123.2017.12025 Abstract ( 329 )   [Full Text(HTML)] () PDF (1474KB) ( 45 )   A two-dimensional reversed-phase liquid chromatography (2D-RPLC) method was established to separate lignan components and pure compounds from Schisandra chinensis. This method was based on the modules of separation-enrichment and self-developed with independent intellectual property rights. First, a C18 column (250 mm×4.6 mm, 5 μm) was used as the analytical column. A water-methanol mixture was selected as the mobile phase. Separation resolution and retention time were selected as indexes. Gradient chromatography of the lignan extracts was repeated four times and the information was input into XTool, a chromatographic separation software. The conditions for the first-and second-dimensional chromatographic separation were optimized by XTool. Then, linear amplification was used for preparative chromatography. C18 column (250 mm×30 mm, 10 μm) was selected as the first-and second-dimensional separation column. The C18 columns (80 mm×30 mm, 10 μm) were selected as enriching columns, and water was chosen as the diluent solution. Lignans from Schisandra chinensis were separated and purified by 2D-RPLC. Finally, nine lignan components were obtained by the first-dimensional separation. Totally, 20 high-purity compounds, containing six monomers, were obtained by the second-dimensional separation. Experimental results showed that this method has good reproducibility. This method thus allows for the systematic separation of lignans from Schisandra chinensis.

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Separation and purification of compounds from piper kadsura using preparative reversed-phase liquid chromatography and preparative supercritical fluid chromatography XIN Huaxia, PENG Ziyue, JIANG Dasen, FU Qing, JIN Yu, LIANG Xinmiao 2018, 36 (5):  474-479.  DOI: 10.3724/SP.J.1123.2017.11054 Abstract ( 451 )   [Full Text(HTML)] () PDF (933KB) ( 101 )   A method based on preparative reversed-phase liquid chromatography (prep-RPLC) and preparative supercritical fluid chromatography (prep-SFC) was developed for the separation and purification of compounds from piper kadsura. A pretreatment method was first developed, including methanol extraction, water precipitation, petroleum ether extraction, etc. Chlorophyll and other strong polar impurities were removed from the piper kadsura samples, and the target components were enriched in petroleum ether extracts. The piper kadsura samples were separated into 18 fractions on a Unitary C18 column (250 mm×20 mm, 5 μm) with water and methanol as the mobile phases. Then, the SFC parameters, including the column, modifier, temperature, and backpressure were optimized. The optimized conditions for prep-SFC were as follows:XAmide column (250 mm×20 mm, 5 μm), methanol as the modifier, 30℃ column temperature, and 15.0 MPa backpressure. Because of the good orthogonality of RPLC and SFC, six highly pure compounds were isolated, including kadsurenone, wallichinine, denudatin B, pellitorine, 2E-decenoic acid N-isobutylamide, and futoxide.

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Impact of carrier flow composition on membrane adsorption and aggregation of ovalbumin in asymmetrical flow field-flow fractionation LIANG Qihui, YANG Yi, SHAO Bing, GAO Ye, SONG Yu, HAN Nanyin 2018, 36 (5):  480-486.  DOI: 10.3724/SP.J.1123.2017.12014 Abstract ( 308 )   [Full Text(HTML)] () PDF (985KB) ( 99 )   Asymmetrical flow field-flow fractionation (AF4) is a kind of moderate separation technology for the analysis of macromolecules, including proteins with a wide range of sizes. In the separation channel, the membrane adsorption and aggregation of proteins affected by the carrier fluid (CF) composition lead to changes in analyte recovery and size distribution, thereby restricting the application of AF4 to biomolecules. Different pH levels (6.2, 7.4, 8.2), several types of cations (Na+, K+, Mg2+) and various ion strengths (0-0.1 mol/L)were studied to demonstrate the influence of carrier fluid composition on the membrane adsorption and aggregation of proteins. The results revealed the following:a) higher ion strength of CF resulted in a greater degree of membrane adsorption and aggregation; b) the zeta potential, determined by the pI of the protein and the pH of the CF, influenced the adsorption and aggregation; c) divalent cations (Mg2+) caused serious adsorption and aggregation. The experimental results can help us achieve better recovery and mitigate aggregate formation by using the optimal CF components in future AF4 studies. Moreover, the findings indicate that AF4 would find extensive application in protein biochemistry assays.

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Simultaneous determination of 12 monohydroxylated polycyclic aromatic hydrocarbon metabolites in human urine by ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry FU Hui, HU Xiaojian, CHEN Xi, LIN Shaobin 2018, 36 (5):  487-492.  DOI: 10.3724/SP.J.1123.2017.12029 Abstract ( 367 )   [Full Text(HTML)] () PDF (918KB) ( 69 )   An efficient and accurate method was developed for the simultaneous determination of 12 monohydroxylated polycyclic aromatic hydrocarbon metabolites in human urine. A 10.0-mL urine sample was hydrolyzed by enzyme and extracted using solid phase extraction. The metabolites were separated on an Acquity UPLC®HSS T3 column (100 mm×2.1 mm, 1.8 μm) with a mobile phase comprising methanol and water. The analytes were detected by electrospray ionization (ESI)-MS/MS in negative mode and multiple reaction monitoring (MRM) mode. The linear ranges of the 12 metabolites were 0.04-20.0 μg/L with correlation coefficients above 0.99. The detection limits were in the range of 0.01-0.41 μg/L and the recoveries were 80.0%-105%. The intra-group relative standard deviations (RSDs) were less than 9.12% and the inter-group RSDs were less than 19.7%. This method was applied to the analysis of 100 urine samples and the results showed that the method was simple, sensitive and selective.

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Identification of dalbergia odorifera and dalbergia spp by solid phase microextraction-gas chromatography-mass spectrometry HOU Sirun, HUANG Xiaolan, MA Yanfang, HUANG Fang, LIN Xiaoshan, MA Yefen, ZHU Zhixin, LUO Huitai, WU Huiqin 2018, 36 (5):  493-498.  DOI: 10.3724/SP.J.1123.2017.11058 Abstract ( 485 )   [Full Text(HTML)] () PDF (795KB) ( 99 )   In addition to species identification, the volatile components of dalbergia odorifera and dalbergia spp, were investigated by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). Small amounts of powder samples were acquired by drilling from dalbergia, then the volatile components of the powder samples were concentrated by SPME, and separated by AB-FFAP polar capillary GC column. Of all the volatile components, twenty types were identified, and two pairs of them, 2-(1,1-dimethylethyl)-5-heptyl-5-methyl-1,3-dioxolan-4-one and 2,6,10-trimethyl-7,10-epoxy-2,11-dodecadien-6-ol, 2-methylbutylidene-cyclopentane and 2-(5-methyl-furan-2-yl)-propionaldehyde, could be considered specific volatile components for the identification of dalbergia odorifera and dalbergia spp, and the relative contents of these two pairs were compared for the species identification analysis. The method has the advantages of less sample requirement, simple operation, and no construction damage. The method is suitable for the research of volatile components and species identification analysis of dalbergia odorifera and dalbergia spp, and has broad prospective application in the analysis of furniture, art collections and raw wood of dalbergia.